Space

The Space Unit is an organisation of hobbists devoted to the collection
and study of covers and stamps issued on space themes. It has a world wide
membership and is the largest independent astrophilatelic society in the
world.

Space commemorative event covers are commemorative envelopes that are postmarked on the day a space event occurs. ... Additional space commemorative event covers could be from participating tracking stations, tracking ships, recovery ships, land recovery operation headquarters, etc. ... can also include covers with special cancels, such as for space trek conventions, cancels honoring previous astronauts or space anniversaries, etc. So there are all types of event covers in existence. ...

"I was located on Grand Turk Island, in the West Indies, where the U.S.A.
had a Project Mercury tracking station and I was working at the telemetry
site operating electronics equipment. There was also a small but well
staffed Mercury hospital on the island as astronaut John Glenn would be
brought there after orbiting the earth and splashing down in nearby waters.
...

"I am always happy to be able to combine two of my
hobbies -- in this case, meteorite collecting and stamp
collecting. So far I have located only the following
stamps commemorating meteorites or meteorite
impacts. If you know of any others,
please let me know. " (he also features some Roman coins depicting a metorite: the sacred Stone of Emesa. aj. 3/2001

Science

Astronomy and Cosmology
Instruments and Measurements
Mathematics and Computation
Chemistry
Evolution and the Fossil Record
Biology
Heredity and the Genetic Code
Physics
Electromagnetic Theory and Light
Modern Physics
Geology and Mapping
The Nobel Prizes
References